Lawrence Berkeley National Laboratory
Towards the goal of half-Angstrom resolution: From 0AM to TEAM
- Author(s): O'Keefe, Michael A.
- et al.
Sub-Angstrom resolution is important for nanotechnology. As researchers design and build artificially-structured nanomaterials such as semiconductor devices, ceramic coatings, and nanomachines that operate at the atomic level, the requirement for "seeing" what has been built becomes more crucial. Better resolutions (nearer to 1 Angstrom) are required to "see" lighter atoms such as carbon, nitrogen and lithium. Defects and non-periodic structures can require 0.5 Angstrom. Once its spherical aberration has been corrected, a microscope's resolution is controlled by its information limit. The one-Angstrom microscope (O Amgstrom M) at LBNL provides Cs-corrected images by using focal-series reconstruction software in combination with a field-emission high-resolution electron microscope (CM300FEG/UT) modified to extend its information limit. The O Amgstrom M has demonstrated the capability for 0.78 Angstrom resolution at 300keV. The Transmission Electron Achromatic Microscope (TEAM) is proposed to reach resolutions of 0.5 Angstrom using hardware correction of Cs in combination with a monochromator (to improve the TEAM's information limit beyond that of the O Angstrom M's 0.78 Amgstrom). Methods employed in the design and implementation of the successful O Angstrom M project have been used to determine appropriate parameters for the TEAM. Calculations show that a Cc corrector is not required for the TEAM to reach 0.5 Angstrom at 300keV or 200keV, provided that energy spreads can be reduced to 0.4eV and 0.2eV respectively. These values allow more substantial beam current than the generally-assumed 0.1eV, resulting in reduced exposure times and better chemical sensitivity.